The invention is directed to a torque controller for an internal combustion engine by controlling intake air quantity based on a state of combustion.
As discussed in Japanese Patent Kokai No. 62-110536, in order to achieve a target engine torque, a target opening degree of an electronic controlled throttle valve is calculated from a lookup table, which defines the target throttle position as a function of target engine torque and engine rotation.
The conventional practice is made on an assumption that the air/fuel ratio is fixed at a predetermined value, for example, at the stoichiometric air/fuel ratio. Therefore, in this case, the lookup table which defines the target opening degree of the throttle valve has settings suitable for the stoichiometric air/fuel ratio. Thus, the conventional practice cannot be applied to the engine which changes the air/fuel ratio according to engine operating conditions.
In recent years, direct-injection gasoline engines have attracted special interest. In such a direct-injection gasoline engine, as discussed in Japanese Patent Kokai No. 59-37236, the combustion mode changes between a homogeneous combustion and a stratified combustion according to the engine operating conditions.
In the homogeneous combustion, fuel is injected during an intake stroke to diffuse the injected fuel so as to form a homogeneous mixture in the combustion chamber. On the other hand, in the stratified combustion, fuel is injected during a compression stroke to form a stratified fuel mixture around a spark plug.